Why (and how) Do Some Animals Poop Pellets?


There has to be a reason, or reasons.

When I’m in the field and come across scat from animals such as deer, elk, pronghorn or rabbits I often wonder why (and how) their poop is in pellet form. Then, by the time I get home I’ve forgotten about it and don’t do the research.

pronghorn 5812 ron dudley Why (and how) Do Some Animals Poop Pellets?

But this photo, taken three days ago on Antelope Island, hasn’t allowed me to forget about it. This buck pronghorn unceremoniously took a dump right in front of me and I’ve found his falling fecal pellets pretty hard to ignore. The lighting is poor on most of the animal but it’s just about ideal on his ‘business end’ where it matters.

pronghorn 5812 ron dudley Why (and how) Do Some Animals Poop Pellets?

There has to be a reason, or reasons, why some animals poop pellets and others, including humans, don’t. The other question is, how in the world are the pellets formed in their digestive tracts? You’d almost think that those animals must have some kind of ‘forms’ similar to ice cube trays, or alternately some kind of sausage making machine, in their colons and/or rectums.

So yesterday I finally did the research and found this explanation from the folks at The Straight Dope so I thought I’d share.

“A legitimate question. Let us deal with the matter as scientists.

A combination of things is involved. The answer lies in large part in the digestive tract itself. In animals such as rabbits, the feces are formed into pellets by the colon, which pushes them out into the rectum rhythmically, leading to a fairly uniform shape and size. Of course, the rectum also plays a role. Some animals have internal muscles that control the process to a degree, such that each fewmet comes out virtually the same size and shape-essentially, the rectum acts a lot like a press (maybe a better analogy would be a sausage-making machine). Caterpillars, which lack a colon or sphincter, derive the shape of their droppings entirely from the rectum, while the dropping shapes of animals such as goats, deer, and rabbits are due to a combination. Horse apples are not quite as consistent, but they’re close. When the feces are more amorphous, only the anal sphincter contributes to the shape; if the sphincter stays open a long time, you tend to get long, unbroken masses, as in humans. The phenomenon doesn’t correlate strictly with a fibrous diet (though the pellets would probably not hold their shape otherwise), since animals like cows and buffaloes have a fibrous diet but most definitely have soupy poop. Obviously, the digestive process itself-which is different in ruminants such as cattle-is also a factor.


So, to recap, the #1 factor is the colon, #2 is the rectum (and possibly sphincter), and #3 is the diet and how it’s digested (that is, those factors which determine the consistency of the feces itself).”

So now you know and so do I. And yes, I feel better.

When you do research like this you never know what you’ll come across. Did you know that spitting antelope pellets is a sport? Check this and this out.

On that alimentary note, Happy Easter!


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Ethan Smith is a seasoned marine veteran, professional blogger, witty and edgy writer, and an avid hunter. He spent a great deal of his childhood years around the Apache-Sitgreaves National Forest in Arizona. Watching active hunters practise their craft initiated him into the world of hunting and rubrics of outdoor life. He also honed his writing skills by sharing his outdoor experiences with fellow schoolmates through their high school’s magazine. Further along the way, the US Marine Corps got wind of his excellent combination of skills and sought to put them into good use by employing him as a combat correspondent. He now shares his income from this prestigious job with his wife and one kid. Read more >>